The present invention relates to a method for supplying a chemical or chemical compound in a fibrous web machine, in which method the chemical or chemical compound is supplied via at least two displacement pumps to a common supply line, through which the chemical or chemical compound is supplied to the operating device of the fibrous web machine, and in which each displacement pump has a corresponding electric actuator.
In addition to this, the present invention also relates to an apparatus for supplying a chemical or chemical compound in a fibrous web machine, the apparatus comprising two displacement pumps, by means of which the chemical or chemical compound can be supplied to a common supply line, through which the chemical or chemical compound can be supplied to the operating device of the fibrous web machine, and in which each displacement pump has a corresponding electric actuator.
As a part of the fibrous web machine, for example in paper machines, may be a system which processes chemicals or chemical compounds or similar masses, that is connected through the supply system to the fibrous web processing machine proper. In the case of a coating machine, the supply system is the machine cycle which is connected, for example, to the paper coating machine, wherein the coating compound (a chemical compound) is applied with an applicator, for example a curtain coater (including, e.g. spray, blade and roller coating devices), on the surface of the paper. The coating compound is supplied to the coating machine, for example, by feeding it from a tank by means of one or more displacement pumps to the feed channel, which is in turn connected to the coater.
When a process fluid supplied through more than one pump to the same process connection is concerned, a problem arises from the pulsating pumping of the fluid by the displacement pumps. This creates pressure pulses in the process flow rate and fluctuation in the volume of flow. As an example could be mentioned that this results in unfavourable changes in the amount of coating compound supplied to the coating machine via two pumps, and further in the deterioration of the quality of the surface of the paper.
Another problematic area are changes in process conditions, for example, the changing of chemicals or power cuts, in connection with which the correct resynchronization of two or more pumps is rather difficult.